Method for preparing {60 ,{60 {40 -dicumyl from{60 -cumene hydroperoxide

ABSTRACT

Cumene hydroperoxide is decomposed in the presence of cumene at an elevated temperature and superatmospheric pressure to form Alpha , Alpha &#39;&#39;-dicumyl, cumyl alcohol, and water.

United States Patent Inventor James C. Wygant Creve Coeur, Mo.

Appl. No. 860,784

Filed Sept. 24, 1969 Patented Nov. 16, 1971 Assignee Monsanto Company St. Louis, Mo.

lVlETHOD FOR PREPARING iz,a'-DICUMY L FROMa-CUMENE HYDROPEROXIDE References Cited OTHER REFERENCES Von George A. Twigg et al., Erdolund Kohle, Vol. 15, pp 74- 78, 1962.

The Chemistry of Hydrocarbons, Ed. Brooks et al. Vol. 2, pp. 339- 340, Reinhold Publishing, 1955.

Kharasch et al. J. Org. Chem, 15, 763, 1950.

Kharasch et al.,J. Org. Chem., 16, 105, l95l.

K. V. Topchieva et aL, Vestn. Mosk. Univ., Ser. ll Kh.m. l8 (3) 18-23, [963, (Chem/Abs. 59:6166C) Primary Examiner-Delbert E. Gantz Assistant Examiner-Veronica OKeefe Anomeys-Neal E. Willis. J. E. Maurer and Wayne R.

Eberhardt ABSTRACT: Cumene hydroperoxide is decomposed in the presence of cumene at an elevated temperature and superatmospheric pressure to form a,a-dicumyl, cumyl alcohol, and water.

METHOD FOR PREPARING.a,a"-DICUMYL FROM or CUMENE HYDROPEROXIDE BACKGROUND or The INVENTION 1. Field of the Invention This invention relates to the preparation of aromatic hydrocarbons, and more specifically, to the preparation of the compound oz,a'-dicumyl, also known as a,a,a,a-tetramethylbibenzyl and 2,3-dimethyl-2,3-diphenyl butane.

2. Description of the Prior Art Many methods for the preparation of dicumyl are described in the literature. For example, it is known to decompose dicumylperoxide in cumene to fonn dicumyl,-cumyl alcohol, and methane. In another method, cumene is irradiated with ultraviolet light in the presence of a phenyl-radical source to yield mainly benzene, some dicumyl, and a mixture of isomeric isopropylbiphenyls. It is also known to react cumene with carbon tetrachloride in a light-activated reaction to yield I-ICl, CHCh, various chlorination products, and dicumyl. Similarly, photolysis of a solution of cumene and MeHgl yields dicumyl and methane. In yet another method cumene is reacted with tertbutyl peroxide to form dicumyl, tert-butyl alcohol, and acetone.

The above-described methods typically suffer from one or more disadvantages such as low yields,'difficult reaction conditions, or expensive raw materials. For example, the reaction of tert-butyl peroxide with cumene to form dicumyl proceeds with good yields, but the process is economically unattractive due to raw material costs.

It is also known in the literature that a-cumene hydroperoxide may be thermally decomposed to emf-dicumyl, this reaction being described by Kharasch et al. in the Journal of Organic Chemistry, Vol. 16, page H6 (1951). In this process however, the emf-dicumyl is recovered as part of a high-boiling residue at only percent yield. The present invention describes a method whereby a-cumene hydroperoxide may be thermally decomposed to provide a,a'-dicumyl economically and in good yield.

SUMMARY OF THE INVENTION A process for the production of a,a-dicumyl wherein cumene hydroperoxide, either alone or in solution with cumene, is added to a reaction zone containing a charge of cumene under superatmospheric pressure and at a temperature in excess of 175 C. The rate of addition of the cumene hydroperoxide is regulated to maintain the concentration of unreacted cumene hydroperoxide in the reaction zone at less than about 1 percent by weight. The reaction is discontinued before the molar ratio of cumene hydroperoxide to total cumene charged to the reactor exceeds about 1 to 3, and the a,a'-dicumyl product is recovered from the reaction mass by distillation and recrystallization.

DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with this invention, it has now been discovered that high yields of Idicumyl can be obtained by reacfing cumene hydroperoxide, hereinafter referred to as CHP, with an excess of cumene under conditions such that the concentration of unreacted CHP in the reaction medium does not exceed about 1 percent by weight. Under the conditions of this invention, the CH? is found to react quickly with the eumene to form dicumyl, cumyl alcohol, and water with a minimum amount of side products.

The conditions of reaction are defined by temperature, molar ratio of CH? to cumene, and rate of addition of CH? to the reactor. The reaction is most conveniently conducted in a semicontinuous mode of operation, with the CI-lP being metered into a reactor precharged with cumene. After a predetermined amount of CHF has been added to the reactor, as determined by the limit of molar ratio of CHP to cumene, the reactor contents are processed for recovery of the a,a'- dicumyl.

The temperature of the reaction is preferably maintained within the range of 175 to 250 C., and more preferably within the range of 200 to 230 C. Since cumene boils at 154 (3., pressure is necessary to achieve these higher reaction temperatures. it is convenient to equip the reactor with a pressure relief valve set at about 75 p.s.i.g. As the reaction proceeds, the pressure increases from an initial value of about 50 p.s.i.g. to the relief pressure, at which time a mixture of water and gaseous byproduct (methane) is continuously vented. If desired, the reactor may be pressurized with nitrogen at the start of the reaction to reduce the initial rate of reflux.

The molar ratio of Cl-H to cumene is preferably limited to not exceed 1 to 3, and a ratio of less than about I to 5 is generally preferred. It has been found that large excesses of cumene promote higher yields of dicumyl, and that the maximum excess of cumene commensurate with economic and equipment considerations is therefore desirable.

The molar ratio of CHP'to cu'mene is based upon the total moles of CHP and cumene involved in the reaction. All the cumene may be precharged to the reactor, or a part may be precharged with the remainder being added concurrently with the CHP. Either method is satisfactory, the only requirement being that a sufficient amount of cumene be precharged to the reactor to provide an initial reaction medium.

As previously discussed, the rate of addition of CHP must be controlled to prevent any substantial accumulation of undecomposed peroxide in the reactor. Generally, it is preferable to maintain the peroxide level at less than 1 percent. The maximum rate of addition of Cl- P to the reactor is largely de pendent upon the particular variables of individual systems, such as reactor size, bafile design, agitator design and speed, point of entry of CH? (above or below surface), method of entry of CH? (single pipe, slinger ring or other distribution system,) concentration of CHP feed if diluted with cumene, reaction temperature, etc. These variables all affect the rate of mixing and decomposition of the CHIP, and therefore the maximum rate of addition of CH? to the reactor will vary according to the efiect of these variables. A well mixed reactor at a temperature of about 220 C., for example, may be operated at a substantially higher CHP addition rate than a poorly mixed reactor at a lower temperature. As a practical consideration, the maximum Cl-IP addition rate must be separately determined for each individual system.

In a preferred embodiment of the present invention, the equilibrium concentration of undecomposed CHF in the reaction zone during the CH? addition period has been found to be less than 0.5 percent. Although the concentration of peroxide in the reactor may exceed 1 percent during the initial period of operation, it is preferred that the equilibrium concentration be maintained at less than about l percent during the bulk of the reaction period. After all the CHI has been added to the reaction, the mixture is held at the reaction temperature for 30 minutes or longer until the peroxide content decreases to less than about 0.1 percent. The excess cumene and the cumyl alcohol are removed by distillation leaving a dicumyl residue which may be recovered as a white solid by crystallization from ethyl alcohol.

The concentration of CH? in the reaction zone may be conveniently determined according to the procedure given in Quantitative Organic Analysis via Functional Groups, by Siggia, pp. -101, 1949, entitled lodometric Determination of Peroxides."

The method of instant invention is further illustrated by the following examples which are intended to be illustrative only and not limiting of the scope of the invention.

EXAMPLE A series of runs were made in a l-liter stainless steel autoclave equipped with propellor-type agitator, dip-tube with valve for sampling, pressure gauge, and reflux condenser. The autoclave was heated with an electric heating mantle. A relief valve set for 75 pounds was mounted atop the reflux condenser.

Cumene was charged to the autoclave through a charging port. The port was closed, and the autoclave was stirred and heated to the desired operating temperature. When the specified temperature was reached, the inlet valve was opened tion rate. It is also contemplated that, by heating a separate steam of cumene to reaction temperature, then metering a CH? feed into this stream with provision for required mixing and reaction time, the semicontinuous process described and cumene hydroperoxide was metered into the reactor with could easily be converted to a fully continuous process. a variable flow piston pump equipped with a volumetrically The use of peroxide decomposition catalysts is also concalibrated feed reservoir. As the reaction proceeded the pressidered to be within the scope of the present invention. These sured increased, and at 75 pounds a mixture of methane and catalysts are well known for their function, and include such water vapor vented through the relief valve. Peroxide concenmildly basic materials as the alkali earth oxides and acetates, tration of the reaction mixture, monitored by periodic samand the alkali metal carbonates, bicarbonates, and acetates. pling through the dip tube, was found to be consistently less The decomposition of CH? to a,a'-dicumyl should be conh n perce t ducted in the absence of any mineral acids. The addition of When the desired amount of cumene hydroperoxide had small amounts of mildly basic materials therefore, in addition been added, the pump was stopped. Alter an additional one- 5 to their catalytic efi'ect, also serve to neutralize any trace half to 1 hour at operating temperature, heating was stopped. amounts of mineral acids which might be present. The mineral wh cool h autoclave was vented d d d h acids, if not inhibited, promote the formation of phenol and product removed. The reaction mixture was filtered and one by decomposition of CHP, and thereby drastically vacuum-stripped through a short Vigreux column to remove reduce the yi l ofdicumylexcess cumene d byproducts yl l hol d The dicumyl produced by the method of this invention has acetophenone. The residue, a yellow oil, crystallized on coolmany uses, and may for example be hydrogenated to form an ing. It was recrystallized from about 3 parts of ethyl alcohol to xi l ly Stable base Stock for functional fluids: i ld h product di l as a hit r t lli lid, Having thus described and defined my invention, what 1 l l4l 16. The conditions of reaction and the yield of a,a'- Claim is: dicumyl for each run wereasfollows: l. A process for the preparation of dicumyl which com- Reactor Pro- Reactor feed, Molar Reactlon Feed charge moles Total ratio temperaaddi- Dicumyl moles of moles CH1: ture, time, yield, Run cumene car Cumene cumene cumene C hours percent {a 2. 0 0. 2 0. 4 2. 4 1:12 180 5. s 27. 0 Series A b 2.0 0.2 0.4 2.4 1:12 200 4.1 33.9 0 2.0 0.2 0.4 2.4 1:12 215 3.5 44.8 {d 2. 0 0. 4 0. 4 2. 4 1:0 210 2. 0 27. 7 Series B e 2.0 0.4 0.4 2.4 110 220 2.0 31.8 r 2. 0 0. 4 0.4 2. 4 1:6 230 2.0 30.1 g 2. 0 0. 4 0. 4 2. 4 1:6 215 6. 0 33. 8 h 1. 2 0. 4 1. 2 2. 4 1:6 215 4. 0 32. 7 Series C. i 2.0 0.4 0.4 24 1:0 215 2.5 35.7 j 2.0 0.4 0.4 24 1:6 220 2.0 31.8 k 2. 0 0. 4 0.4 2. 4 1:0 220 4. 0 5 ll. 1'35 3 ti ii; 533 2:3 iii a: t: a: :22 a 1.22

The data in Series A above show the effect of reaction temprises heating cumene hydroperoxide with cumene at a temperature on dicumyl yield. Specifically, the data show that, at perature above about 175 C. and at superatmospheric presa 1:12 molar ratio of CHP: cumene, the dicumyl yield is insure the ratio of cumyl hydroperoxide to cumyl being less than creased from about 28 percent to about 45 percent by increasl to 3. ing the reaction temperature from 180 C. to 215 C. Similar 2. A process of claim H wherein the cumene reactant is data for a 1:6 molar ratio of CHP: cumene presented in Series re harged to a reaction zone and heated to reaction tempera- 3 also Show that g yi l are Obtained at and C ture, and the cumene hydroperoxide is added thereto at a rate The CHP addition fate was not Critical at the W615 determined to maintain the concentration of cumene P y in this p as evidenced y comparison of hydroperoxide in the reaction zone at less than about 1 per- (g), (h) and (i) of series C, wherein the CHP addition time cent b i h was decreased from 6 hours to 110111? with Significant 3. A process of claim 2 wherein the reaction temperature is change in dicumyl yield. Runs (j) and (k) of this Series between 200 C, d 230 C Pmduced results essentially equivalent to of runs 8 4. A process of claim 2 wherein the molar ratio of cumyl (h) and at the g higher temperamle of hydroperoxide to cumene is between about 1 to 6 and 1 to 12. C. Run in Series D Shows h operation with 8 feed 5. A process of claim 2 wherein the concentration of cu- Stream consisting solely of CH? and with a total molar ratio of mene hydroperoxide in the reaction zone is maintained at less CHP: cumene of 1:6 provides a good yield of dicumyl. Run h b t 5 percent by weight,

(" Shows a Slight decrease n yie d h n h HPI m n 6. A process of claim 2 wherein a part of the cumene reacl'atl'o was decreased to tant is charged to the reaction zone and the remainder is Series E data are presented for comparison t Show h fadded thereto concurrently with the cumene hydroperoxide. fect of operating at a reaction temperature below the 7. A process for the preparation of a,a'-dicumyl which minimum limit defined by the invention. At a temperature of comprises 155 C., the yield of a,a-dicumyl was only about 16 percent, a. charging a reaction zone with a first reactant comprising whereas when operating within the temperature limits of this a-cumene, invention, yields in excess of 30 percent are generally obb. heating said first reactant under pressure to a temperatained. ture above about 175 C.,

The preceding examples serve to illustrate the practice of c. adding to said heated first reactant a second reactant the present invention, but the invention is not intended to be comprising a-cumene hydroperoxide, and limited thereto. For example, given the knowledge of this ind. discontinuing the addition of the second reactant before vention, it is within the ability of one skilled in the art to modithe molar ratio of cumene hydroperoxide to cumene fy the described procedure by employing a variable CHP addiadded to the reactor exceeds 1 to 3,

8. A process of claim 7 wherein the reaction temperature is maintained between 200 C. and 230 C.

9. A process of claim 7 wherein the second reactant comprises a mixture of a-cumene hydroperoxide and a-cumene.

l I I! I! I! 5 

2. A process of claim wherein the cumene reactant is precharged to a reaction zone and heated to reaction temperature, and the cumene hydroperoxide is added thereto at a rate determined to maintain the concentration of cumene hydroperoxide in the reaction zone at less than about 1 percent by weight.
 3. A process of claim 2 wherein the reaction temperature is between 200* C. and 230* C.
 4. A process of claim 2 wherein the molar ratio of cumyl hydroperoxide to cumene is between about 1 to 6 and 1 to
 12. 5. A process of claim 2 wherein the concentration of cumene hydroperoxide in the reaction zone is maintained at less than about 0.5 percent by weight.
 6. A process of claim 2 wherein a part of the cumene reactant is charged to the reaction zone and the remainder is added thereto concurrently with the cumene hydroperoxide.
 7. A process for the preparation of Alpha , Alpha ''-dicumyl which comprises a. charging a reaction zone with a first reactant comprising Alpha -cumene, b. heating said first reactant under pressure to a temperature above about 175* C., c. adding to said heated first reactant a second reactant comprising Alpha -cumene hydroperoxide, and d. discontinuing the addition of the second reactant before the molar ratio of cumene hydroperoxide to cumene added to the reactor exceeds 1 to 3,
 8. A process of claim 7 wherein the reaction temperature is maintained between 200* C. and 230* C.
 9. A process of claim 7 wherein the second reactant comprises a mixture of Alpha -cumene hydroperoxide and Alpha -cumene. 